diff --git a/scene/3d/mesh_instance_3d.cpp b/scene/3d/mesh_instance_3d.cpp
index 7b3a0820f12..b997c64b295 100644
--- a/scene/3d/mesh_instance_3d.cpp
+++ b/scene/3d/mesh_instance_3d.cpp
@@ -319,6 +319,7 @@ Ref<Material> MeshInstance3D::get_active_material(int p_surface) const {
 }
 
 void MeshInstance3D::_mesh_changed() {
+	ERR_FAIL_COND(mesh.is_null());
 	materials.resize(mesh->get_surface_count());
 }